1. Field of the Invention
The present invention relates to a control unit for a construction machine, and more particularly, to a control unit for a construction machine capable of operating while switching operation mode between a low-speed operation mode and a high-speed operation mode.
2. Description of Relevant Art
A conventional control unit for a construction machine of this kind will be explained with reference to FIGS. 2, 3 and 7. FIG. 2 is a diagram showing performance of a pump, FIG. 3 is a diagram showing performance of an engine. These drawings are used also for explaining an embodiment of the present invention. FIG. 7 is a diagram of a control circuit of mainly a hydraulic shovel.
In FIG. 7, a reference number 12 represents a first hydraulic pump 12, and a reference number 13 represents a second hydraulic pump. Control valves 1 to 8 for various actuators such as a boom, an arm a bucket and a cylinder are connected to oil paths of the first and second hydraulic pumps 12 and 13. The first and second hydraulic pumps 12 and 13 are driven by an engine 19. A fuel-injection amount and a fuel-injection timing of the engine 19 are adjusted by a control actuator 20 of an engine governor. The control actuator 20 of the engine governor is operated by a command signal from a controller 21. Discharged oil from the first and second hydraulic pumps 12 and 13 is controlled by an actuator 15 comprising a solenoid proportional valve. The actuator 15 is operated by a command signal from the controller 21.
The construction machine is constructed such that it can be operated while switching operation mode between a low-speed operation mode and a high-speed operation mode. The switching operation is carried out by manually operating, by an operator, an operation-mode selecting switch 26 connected to the controller 21. In the drawing, a reference number 14 represents a pilot pump, and a reference number 22 represents a battery.
As shown in FIGS. 2 and 3, the operation mode comprises A mode having excellent speed and power (which will be referred to as xe2x80x9chigh-speed operation modexe2x80x9d hereinafter), and B mode suitable for low fuel-consumption and fine operation (which will be referred to as xe2x80x9clow-speed operation modexe2x80x9d hereinafter). The operator manually operate the operation-mode selecting switch 26 to select desired either one of the operation modes. The controller 21 recognizes ON and OFF of the operation-mode selecting switch 26. When the operation-mode selecting switch 26 is ON for example, the controller 21 judges that the high-speed operation mode was selected, the controller 21 sends a command signal to the actuator 20 of the engine governor which controls the engine 19, thereby switching the engine 19 to the high-speed operation mode. At the same time, the controller 21 also sends a command signal to the actuator 15 which controls discharging oil of the first and second hydraulic pumps 12 and 13, and the discharge oil of the first and second hydraulic pumps 12 and 13 is switched, by the actuator 15, to high output state which is suitable for the high-speed operation mode.
When the operation-mode selecting switch 26 was switched to OFF manually by the operator, the controller 21 sends a command signal to the actuators 20 and 15 so that the engine 19 as well as the first and second hydraulic pumps 12 and 13 are switched to the low-speed operation mode, and the operation in the low-speed operation mode is carried out.
When the operation-mode selecting switch is switched to the high-speed operation mode by the operator""s manual operation, since the high-speed operation mode is excellent in speed and power, the mode is suitable for operation requiring high speed or great load. However, during a series of operation in the high-speed operation mode, even when the construction machine is operating with low load or under fine control, such an operation is carried out while keeping the high engine output and thus, fuel is consumed wastefully. In order to avoid such a wasteful fuel consumption, the operation-mode selecting switch must be switched to the low-speed operation mode by the manual operation whenever it is required. Such a switching operation is troublesome. Generally, the operator does not carry out the switching operation, and fuel is consumed wasteful as described above.
When the operator switches the operation-mode selecting switch 26 to carry out operation in the low-speed operation mode, the low-speed operation mode is excellent for fine operation by the operator and reduction in fuel, but when it is desired to operate the machine faster during the series of operation in the low-speed operation mode, or when greater power is required, speed and power of this mode are insufficient, and this mode can not satisfy the speed and power that the operator requires. It is extremely troublesome to manually switch the operation-mode selecting switch to avoid this each time.
In the construction machine which is operated while selecting either one of the high-speed operation mode and the low-speed operation mode, there is a technical problem to be solved for satisfying both the low fuel consumption of the engine and appropriate operation speed without troublesome switching operation of the operation-mode selecting switch by manual operation of the operator as in the convention technique, and it is an object of the present invention to solve the problem.
The present invention has been proposed to achieve the above object, and the invention provides a control unit for a construction machine comprising a first hydraulic pump and a second hydraulic pump driven by an engine, in which control valves for various actuators are connected to oil paths of the hydraulic pumps, the control valves are operated by a remote-control valve, an operation mode of the construction machine can be switched to either one of a low-speed operation mode and a high-speed operation mode, wherein when the construction machine is operated in the low-speed operation mode and when a pressure sensor detects an operating speed of an operating lever of the remote-control valve and the detection value exceeded a predetermined value, the operation mode is automatically switched from the low-speed operation mode to the high-speed operation mode by a command signal from a controller: a control unit for a construction machine comprising a first hydraulic pump and a second hydraulic pump driven by an engine, in which control valves for various actuators are connected to oil paths of the hydraulic pumps, the control valves are operated by a remote-control valve, an operation mode of the construction machine can be switched to either one of a low-speed operation mode and a high-speed operation mode, wherein when the construction machine is operated in the low-speed operation mode and when the sum of detection values detected by pressure sensors respectively provided for detecting pressures of the first and second hydraulic pumps exceeded a predetermined value for a predetermined time or longer, the operation mode is automatically switched from the low-speed operation mode to the high-speed operation mode by a command signal from a controller: a control unit for a construction machine comprising a first hydraulic pump and a second hydraulic pump driven by an engine, in which control valves for various actuators are connected to oil paths of the hydraulic pumps, the control valves are operated by a remote-control valve, an operation mode of the construction machine can be switched to either one of a low-speed operation mode and a high-speed operation mode, wherein when the construction machine is operated in the high-speed operation mode and when a pressure sensor detects a hydraulic pressure of the hydraulic pump connected to a boom and the detection value becomes equal to or lower than a predetermined value, the operation mode is automatically switched from the high-speed operation mode to the low-speed operation mode by a command signal from a controller: a control unit for a construction machine comprising a first hydraulic pump and a second hydraulic pump driven by an engine, in which control valves for various actuators are connected to oil paths of the hydraulic pumps, the control valves are operated by a remote-control valve, an operation mode of the construction machine can be switched to either one of a low-speed operation mode and a high-speed operation mode, wherein a radiator water-temperature sensor for detecting a water temperature of a radiator of the engine is provided, and when a detection value of the radiator water-temperature sensor reached a value of warming-up of the engine, the controller sends a command signal which enables the construction machine to operate in the low-speed operation mode or the high-speed operation mode: a control unit for a construction machine comprising a first hydraulic pump and a second hydraulic pump driven by an engine, in which control valves for various actuators are connected to oil paths of the hydraulic pumps, the control valves are operated by a remote-control valve, an operation mode of the construction machine can be switched to either one of a low-speed operation mode and a high-speed operation mode, wherein a hydraulic oil sensor for detecting a temperature of hydraulic oil in the first and second hydraulic pumps is provided, and when a detection value of the hydraulic oil sensor reached a value of warming-up of a hydraulic system, the controller sends a command signal which enables the construction machine to operate in the low-speed operation mode or the high-speed operation mode: and a control unit for a construction machine comprising a first hydraulic pump and a second hydraulic pump driven by an engine, in which control valves for various actuators are connected to oil paths of the hydraulic pumps, the control valves are operated by a remote-control valve, an operation mode of the construction machine can be switched to either one of a low-speed operation mode and a high-speed operation mode, wherein pressure sensors are provided in pilot oil paths of the first and second hydraulic pumps, and when the pilot oil paths were cut off by switching operation of a running control valve during running of the construction machine and a oil pressure detected by the pressure sensor was increased, the controller sends a command signal which enables the construction machine to operate in the low-speed operation mode or the high-speed operation mode.